Metallurgical process



July 1', 1930. QR. n. PIKE 1,769,604.

` METALLURG I CAL PROCES Sv I Original Filed Sept. 23. 1925 zf 1 l y i J INVENToR.

A TTORN YS.

.Patented July 1,1930

UNITED STATES PATENT OFFICE ROBERT D. PIKE, F IPIEDMOT, CALII'OBNIA nETALLUBGIcALrnocnss ,Application mea september 2a, 1925, serial. no. 58,012. Renewed February 27', ma.

This invention relates to a process for recovery of metals from a wide variety of ores and concentrates with production of electrolytic iron. It has been demonstrated that 5 metals are dissolved from sulphide minerals to a greater or lesser extent by solutions con-` taining ferrie salts such as a chloride or sulphate, with the consequent reduction of the ferric salt to the corresponding ferrous salt and the precipitation Yof elemental sulphur; and that the ferrous solutions c/an be treatedl ina diaphragm electrolytic cell for the regeneration of the ferrie salt and the consequent deposition of electrolytic iron. However, up to the present time, unsolved ditli-A 1 culties have prevented the successful commercial application of a process of the above general description. p

The rst of these unsolved diliiculties is the sluggishness of the ferrie solutions as solvents. Some fewr lsulphide minerals are attacked With fair rapidity and completeness, While others are attacked but slowly and incompletely. All results of work to date, in.-

cluding my own, show that with all sulphide minerals ferrie chloride is a more ac tive s olvent than ferrie sulphate, but that the former is not, in most cases, active enough to be considered of itself, alone, a satisfactory commercial solvent for many important sulphide minerals," such, for example, as chalcopyrite.

On this account, and because ferrous chloride is a more satisfactory electrolyte in the electrolytic iron cell, the chloride is to be preferred over thesulfate, and my present process .is particularly adapted to the use of a chloride leach and electrolyte, but can also be used, if desired, with a sulfate leach. The superiority of the chloride leach and elecchloride; and the only way to keep the concentration of such compounds (and possibly others) within allowable limits, is

trolyte oaver the sulphate for the stated rea-- a'- portion of the electrolyte at-each cycle, involving a loss of costly chlorine.

My present invention has-for its object to obtain substantially complete extraction from, and recovery of, metallic values from a wide varietyof sulphide ores and concentrates in a cyclic process which produces pure electrolytic iron andelemental sulphur as byproducts; and to cheaply maintain in standard 'condition the ferrie-ferrousl chlorideleach-electrolyte usedin the process. .e

. In the following description and accompanying drawings I disclose a conventional type of electrolytic cell for converting the ferrous chloride to ferrie chloride an de- .positng electrolytic iron. In my prior Patent' number 1,689,597, issued October 30,

1928, and'ventitled Cell for electro-deposition of metals, filed concurrently herewith, there' is disclosed a method and means for overcomking the other principal unsolvedfdifculty above referred to, namely,rthe successful` large-scale deposition of electrolyti ironV from leach solutions. f

Having outlined the general object of my invention, I will describe,- by way of example but-not for limitation, its application to a Qertain chalCOPyl'ite copper `concentrata of the following analysisg copper 23.25 lr03- 1.10 Insel. '8.56 Iron., 30 CBO .4,9 Silver-- 6.9501, sulphur/529.52 Mgo v .as com-" .2501.

Inv the accompanying drawings,

- Fig. 1 shows one form of flow sheet; and Y' Fig. 2 shows a form providing an alterna.-

tive in one part of the process.

The lreturn vanolyte leach from lytic cells, c'ontaimng about 12% iron (about one-half as ferrous chloride and one-half as ferrie chloride), and at a temperature of 'about 70 C., enters the agitator 1 in a. continuous stream. Into the 'same agitator is fed thaelectrq;

a continuous stream 'o'f the concentrates.

Live steam is introduced, to raise the temperature to C. to 100Y C. Agitation is preferably furnished by a. rubber-covered propeller suspended in the usual manner, and not shown. The concentrates should be finely ground, so that not less than is minus `leach is about two hours.

The agitator is so proportioned to the Workl in hand that the time of residence-of the In this time and under the conditions stated, from 85% to 90% of the copper will be dissolved; 70% to 75% of the iron; 85% to 90% of the silver; and 15% to 20% of the lgold; and corresponding amounts of' elemental sulphur precipitated. The proportion of leach liquor to concentrates is so chosen that the ferrie iron content in the efiluentis 1% to 1.5%. The efiluent passes continuously into `the second agitator 2 (similar to 1), Where itis also heated by steam to 90% to 100%,l and into which is introduced a stream of finely-ground pyrrhotite,vor distilled pyrite, equivalent in weight to about 15% of the original concentrates. The function 'of the pyrrhotite is to reduce the ferrie ironcontent of the liquor to .1% to .2% Without at the same time reprecipitating any appreciable amount of the copperi and silver; although the greater part of the gold, dissolved in agitatorl, is reprecipitated in agitator 2 by the pyrrhotite. Most of the gold remains with the tails from the agitators, while most of the silver remains in solution.

The tails are now dewatered by anyu'sual means illustrated conventionally as classifier 3, thickener 4, and filter 5. The solid residue, or so-called No. 1 tails, represents about half the original weight of concentrates, and contains 30%- to 40% of elemental sulfur, together with sulphur in combination with the undissolved metals. This residue may be treated in sulphur-distilling retorts 7 and the element-al sulphur 'recovered as'refined sulfur in condenser 8. The residue from the retorts goes to roastcr 9, where the metals are partly sulfated Aand partly oxidized; or the sulphur-distilling retorts can be entirely omitted and all the free sulphur burned to SO2 in a roaster. If all the sulphur is burned to SO2 in the roaster, there remains, after deducting the sulphur` necessary for manufacturing acid, required in a later step "of the process, about one pound of sulphur v per pound of original copper in the form of SO2 for making surplus acid for. sale. Whether or not the sulphur-distilling retorts be used, the calcnes from the roaster goto agitator 10, where they are treated with sulphuric-acid and steam, which dissolves prac-p' tically all of the copper, leaving a tail with .2% copper. or less, and also dissolves 30% to' 40% of the iron remaining undissolved after the first, or chloride leach. The amount of iron dissolved in'this leach can be controlled at the will of the operator within limits by varying one or all of the factors of time,

temperature, and strength of acid. The copper is far more soluble than the iron, and if the roast be carried out carefully to produce a maximum amount of copper sulfate, practically all of thecopper is rendered soluble reduced in weight as compared with the.\

original concentrate, and as they contain .80% to 90% of the original gold and about 10% of the original silver, are Virtually a precious-metal-concentrate, and can be treated in any Well-known manner for the recovery of these metals.

The liquor from the sulfate vleach containing copper and ferrie sulfates goes to agitator 14, where it is mixed With calcium chloride, the greater part of which comes from a subsequent step of the process, and the smaller part of which is that amount necessaryto supply chlorine which is lost in the leaching process. The reaction between the copper and ferric sulfates and the calcium ch orides precipitates artificial gypsum and transforms the copper and iron respectively Vto cupi-ic and ferrie chlorides. The gypsum is dewatered 'and Washed by any vusual means, conventionally illustrated as thickener 15 and filter 16. The gypsum can easily be Washed free from copper and iron, and is. a saleable by-p'roductof which about one pound is produced per pound 'of copper in the original concentrates. The chloridized liquor from 14, together with that from agitator 1, or chloride leach, goes to copper cementation drum 6, or other suitable apparatus, for precipitating copper on iron. The cement copper is dewatered in 17, and goes to a refinery. This copper contains about 90% of the original silver. The liquor is next treated with HQS, in a tower 18, to precipitate any traces of zinc and other metals not precipitated by iron. It then goes through thickener 19, and clarifying filter 20, when it is ready to pass to the elcctrolytic iron cells, except that 5% of the whole is discarded at each cycle and goes to the agitator 21, Where enough milk of lime is addedto precipitate all ,of the iron, magnesia, and alumina, as hydrates, at the same time making calcium chloride in solution. The resulting liquor is a water-clear solution containing 12% tov14% CaClg, and goes back to agitator14, asv above mentioned, after vseparation from the precipitate in thickener 22, and filter 23. The hydrate cake from this filter is Waste and contains all the magnesia and alumina dissolved from the original concentrates, as well as about .3 pounds of iron-per pound of original copper. Y

The electrolyte goes to storage tank 24, and thence passes through heater 25 and is delivered 'to electrolytic diaphragm cell 26, at a. temperature of 70 to80 C. The ,anolyte from the` cell goes back directly to the agi tator 1. The surplus, or circulating, catholyte goes through thickener 27, where hydrochloricfacid is` added in suiicient amount to restore the hydrogen ion concentration to .O03 to .0 05 N. The underflow passes to filter 28, the cake .offwhich passes back to.

agitator 1, the filtrate returnin to 24. The overflow 1 goes through clarifying filter 29 and back to 24. .The iron cathodes produced in the cell 26 contain over 99.9% iron,and

are ready for 'the market, vor for further4 treatment. The iron produced .is about 1.75 pounds per pound of original copper in the concentrates.

Fig. 2 illustrates an alternative method of chloridizing'by' roasting instead of by the addition of the calcium chloride solution, asI

above described. By this method the calcines from roaster 9 will contain about one and one-half times as much sulphur as copper. They are then mixed in a pug mill 30,

with all or a portion of the CaCl2 solution, made as above'described in agitator 21, together with the necessary amount of new CaCl2 toxinake up chlorine losses. The material from the pu ,mill is delivered to.any'

suitable form o chloridizing roaster 31.l The gases from the roaster are condensed in a water scrubbing tower 32. The calcines go to aan agitator 33, where they are leached with thetower liquors from 32, and if desired, with a portion of the Aabove-mentioned CaCl2 solution not used in 30; and also', if desired, with a portion of return` anolytev leach from the electrolytic iron cells. The

.addition of free chlorine in any desired' form into agitator 33, as for example,`in the form of bleaching powder, will facilitate the extraction of the gold. v Y v The tails from agitator 33 are dewatered andwashedI in the usual manner, an'd the pregnant liquoris then treated for precipitation of gold and silver, on copper in any usual manner; and copper and lead, if present, are precipitatedon iron.

It will be seen that virtually the only distinction between.y the liow of sheets of Fig.

traction of :the silver 'and gold and lead, if

present, as well as the copper, from anytype of sulphide ore.` already explained, the

tails from agitator 10, Fig. 1, contain'practicallyall of the gold, and about 10% to 15% Vof the silver, and have tobe treated furtherl n for, recovery of. these values.' One method would beto'so conduct the roasting operation .in 9Athatenough sulphur would remain with these tails tomake 'susceptible to chloridizin roasting. They could then be put throug the chloridizing roast in precisely the same manner as just described for the cin- A ders from 9, with resulting complete extraction of silver and gold. Y

My process, as described with either of its modiications, is fully cyclic with vreference,

to chlorine, there being neither loss nor accumulation of this element in the cycle, and at the same time the concentration of magnesia, alumina, and lime, together with zinc,

manganese, and other relatively electro-positive elements, is maintained at a standard condition. Furthermore, this isdone cheaply, lime and sulphur beingthe only chemicals required; but these are recovered in the `form of artificial gypsum, which is a saleable by- By iirst using a ferrie chloride product.

leach upon the raw ore `or concentrates with solution of to 90% copper, and then roasting the residue, I obtain the copper remaining insoluble after the chloride leach,

completely soluble form in sulphuric acid, and then by chloridizing the sulfate solution with calcium chloride I convert all the metals to chlorides before sending the solution on to the electrolytic iron cells, and precipitate the lime out of the solution as gypsum. I obtain the major portion of the calcium' chloride used for chloridizing by treating'V the discarded portion of the electrolyte with lime,

the balance being fresh calcium chloride added to compensate for loss o f chlorine. p

If desired, I maychloridize by. calcium chloride in a chloridizing roast instead -of by the wet way, thus making substantially all thegold and silver vsoluble in ferrie chloride or other chloride leaches.

.The described process is applicable to al-x most .any sulphide mineral or combination Vof same, 'except that I prefer to keep the zinc content of the original' ore 4or concentrate as low aspossible, inasmuch as zinc is re' moved by HzS. It is also preferable to treat concentrates rather than ores, because 1n the latter the content of magnesia, alumina, and

other objectionableelements may be so great as to require an excessively large discard of electrolyte at each cycle.v It is also preferiable that all the minerals treated be in the 'form of sulphides. Most of the so-called oxidized ores of the metals will be soluble in the combinedchloride'and sulfate leaches; but these oresshould be either eliminated entirely or tolerated in the charge only in small. amounts, because they are not as suitable for the cyclic process as are the sulphide j .minerals Having described my process, I` claim as my invention: A `Y 1. A cycliemetallurgical process forextracting -metals from ores containing iron u and copper and recovery of same, which consiste in subjecting lthe ,ore to the leaching pregnant liquors with metallic iron, discardf action of a solution of ferrie chloride, oxidiz ing the tails fromv said leach by roasting, extracting the resulting cindersl to yield the copper and portion of iron and other metals as-sulfatcs, chloridizing the sulfate liquor by addition of calcium chloride., treating thc ing aportion of the leach, and treating this portion with lime to produce calcium chloride,

and electrolyzing the remaining solution containing principally ferrous chloride to produce electrolytic iron and` ferrie chloride for the chloride leach.

2. A cyclic process of extracting metallic values from orcs containing sulphides of iron and/or copper and concentrates containing iron and copper, which consists of subjectf.

ing the ores or concentrates to the leaching action of a solution of ferrie chloride, oxidiz-Y ingthe tails from said leach by roasting, then extracting from the resulting concentrates the metals in the form of sulph-ates, converting the metals to chlorides by chloridization of the sulphate solution with calcium chloride, precipitatingr the calcium sulphate and eleetrolyzingthe remaining solution to produce electrolytic iron and ferric chloride for the leach.

3. In a cyclic process of extracting metallic values from ores containing sulphides of iron and copper, wherein the ores or concentrates are dissolved in ferrie salts and the ferrous solution is electrolyzed to bring about a regeneration of ferrie salts and the electrolytic deposition of iron, the steps of converting the metals to chlorides by chloridization of the sulphate solution with calcium chloride and obtaining'the major proportion of the calcium chloride used for chloridization by treating a portion of the electrolyte with limeand precipitating the lime out of this solution in the form of an artificial gypsum.

4. In a cyclicprocess for treating sulphide ores containing iron and other metals for recovery of electrolytic iron and other metals, leaching the ore with a solution containing ferrie chloride, roasting tails from* this leach, dissolving metals from tails as sulphates, converting said sulphates to chlorides, treating all the resulting liquors for precipitation of substantially all metals except iron, electrolyzing the resulting solution for the production of electrolytic iron and the regen-l solution of the metals which consist in first leaching the unroasted ore with a leach containing erric iron and substantially no acid; and then roasting the residue from this leach anddissolvi'ng the remaining metals as sul-` phates.

6. In a cyclic process for treating sulphide -o lime.

8. In a cyclic process for treating sulphide ores for recovery of their metallic content with the use of separatechloride and sulphate leaching liquors, the steps of chloridizing the sulphate liquors after leaching, and add-ing calcium chloride to the-said sulphate liquors` to supply chlorine to compensate for losses.

.ROBERT D. PIKE. 

